Low drag, corrosion resisting connection and method of forming same



April 19, 1938. N. A. DRAIM 2,114,289

LOW DRAG, CORROSION RESISTING CONNECTION AND METHOD OF FORMING SAME Filed NOV. 2, 1935 D]. l w x4 'f I 5 LL,

. 3 s INVENTOR Z N/CHQLAS A. .DRA/M ATTORNEY Patented Apr. 19, 1938 NECTION SAME AND METHOD OF FORMING Nicholas A. Draim, United States Navy Application November 2, 1935, Serial No. 48,059 6 Claims. .(c 29-148) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 157) This invention relates to riveted connections between plates and between plate and supports therefor, and it has a particular relation to riveted connections for the plates of structures subjected to hydrodynamic and aerodynamic flow, such as the floats or pontoons or seaplanes or the parts of airplanes exposed to air currents.

Heretofore, it has been common practice to unite plates, those of the float of a seaplane for example, with one another or with the internal frame structure, by rivets, the heads of which project beyond .the surfaces of the plates. The rivets may be of the round head, button head, mushroom head or brazier head types. This is practice has been found to be unsatisfactory in such structures for the reasons that they caused a decided drag to the passage of the float through the water and the paint is rapidly scraped off through the abrasive action of solid supports, such as a ramp or beach, thus permitting the rivets to corrode rapidly. Also, when resting on solid supports the protruding heads of the rivets take most of the weight of the seaplane and are forced inwardly, flexing the plates in the vicinity of the rivets. This not only cracks the protective coating of paint around the head of the rivet but also strains the metal of the plates so as to permit moisture to collect at these points and further hasten the corrosion of the rivets. The old meth- 0d of riveting also subjected the rivet to a sheer load of substantial magnitudes and was found to be particularly objectionable when the rivets employed were treated so as to form corrosion resisting anodic films thereon. As a result of the 35 inherent disadvantages enumerated above, a riveted connection made in the usual manner has been found to be particularly susceptible to corrosion and short lived.

Efforts have also been made to overcome the 40 dimculties inherent in exposed rivet heads by employing rivets of flat head type, set in countersunk recesses of proper depth, presenting a flush surface to gaseous or liquid flow. Practical difliculties were even here encountered, in that, when 45 rivets having preformed flat heads beveled to the shank were employed, the process of driving was frequently attended by either damage to the surrounding surfaces of the plate or the rivet head was not packed solidly into its countersink in water-tight condition. When rivets were inserted from the inner surface with the shank extending outwardly and were then upset by the driving tools so as to flll the countersink, the severe working and flowing of the metal of the 55 shank caused splits and cracks to develop at the peripheral edges and outer surface of the head thus formed. This not only resulted in a rivet of unsightly appearance, but one possessing decidedly inferior corrosion resisting properties especially when exposed to salt water as in the case of marine hulls and seaplane floats, for the reason that the water would seep into the cracks and crevices where it was retained by capillary action. Furthermore, an absolutely flush surface, besides being diflicult to obtain practically is still of little protection to the paint, as ascratch starting in the surrounding surface of the plate will continue across the head of the rivet. Moreover, even with a flush rivet, the riveted area presents a region of stiffness, which when the surrounding sheet stock is flexed inwardly by exterior forces it projects outwardly relatively thereto, thus becomingsubject to excessive abrasion.

One of the objects of the invention is to over-' come the disadvantages hereinabove pointed out through the provision of an improved corrosion resisting riveted connection and method of making same, in which the head of the rivet is pre formed and located wholly without a recess or depression in the plate or plates and below the surfaceof the main portion of the plate, so as to protect it from external abrading agencies.

Another object of the invention is the provision of a riveted connection of the character described, in which the plates are formed with conical depressions surrounding the perforation the plate for receiving the preformed head of the rivet and in which the rivet is upset at its inner end, so as to form a head engaging and embracing the apex of the inner conical protrusion, thus reducing sheer strain exerted on the rivet and insuring that the preformed head is packed tightly within its recess, so as to prevent leakage.

With these and other objects in view, as well as other advantages which may be incident to the use of the improvements, the invention consists of the parts and combinations thereof her einafter set forth and claimed, with the understanding that the several necessary elements constituting the same may be varied in proportion and arrangement without departing from the nature and scope of the invention, as defined in the appended claims.

In order to make the invention more clearly understood, there are shown in the accompany-. ing drawing means for carrying the invention into practical'eflfect, without limiting the improve-- ments in their useful application to the particuin: construction, which, for purposes of explanation, have been made the subject of illustration.

In the ac drawing:

1 is a mmentary. elevational view of a rivetedeonnection embodying the present invention:

Fig. 2 is a transverse sectional view taken on line 2-4 of Fig. 1;

Fig. 3isasimilar view ofthe plates afterbeing perforated but before being countersunk; and

' Fig. 4 is a fragmentary, vertical, sectional view of a plate being countersunk by the forming dies.

Referring to the drawing, a riveted connection embodying the invention is shown as comprising two plates i0 and II, having overlapping edges and each bei provided with registering rivet receiving perforations II. The metal of the plates is depressed around each of the perforations so as to form a circular pocket or recess i3 having inclined walls. This depressing of the plates may be accomplished by means of male and female die members it and I5, respectively, the former having a pilot member l6 adapted to engage the perforation l2 and register it with respect to said die members.

The plates l0 and II are secured together in their overlapping position shown and with the pockets ii in the upper plate nesting within the 1 corresponding'pockets in the lowermost plate, by

means of rivets l'l. These rivets are each provided with a relatively flat preformed outer head ll, having a rounded outer surface disposed below the upper edge of the pocket l3, and an inclined inner surface, the latter conforming accurately with the inclination of the walls of the pocket IS. The inner end of the shank I 9 of the rivet I1 is upset so as to form an inner head 20 which closely engages around the inner conicaLprotuberance formed by the depressing operation so as to render the same leakproof. If desired, the rivet l'I may be provided with an anodic film 2i so as to resist corrosion and provide a more desirable base for the coating 22 of paint which has the tendency to collect in the pocket and form a layer thereof of. greater depth than elsewhere, as shown in Fig. 2. This still further fortiflw the rivet against corrosion.

In making the above described riveted connection, the plates l0 and II are arranged in their proper positions and the perforations l2 drilled therein in registering relation (Fig. 3). The

' plates are then separately depressed by means of the dies I4 and I! so as to form the pocket l3,

the pilot member accurately centering the perforations I! with respect thereto (Fig. 4). The plates are then repositioned in their overlapping relation with the pockets l3 nesting and the perforations l2 registering. The rivets i'l' are then inserted in the perforations II with their preformed heads l8 disposed within the pockets i3 and their shanks is are then upset to form the inner heads 20. This upsetting operation is performed by holding a dolly bar having a cavity in the end thereof corresponding in shape to the head l8, against said head and applying the impact blows against the shank l9. If the rivet is vupset inthis manner the head l8 will be packed tightly into the pocket IS without distorting its anodic film or rupturing its surface or edge, and the inner head 2. will flow over and embrace the inner conical protuberance formed by the pocket.

As a result, not only is a water tight connection obtained but the corrosion reskting properties of the rivet materially enhanced.

Other modifications and changes in the proportion and arrangement of the parts, other than thoseshowmmaybemadebythoseskilled inthw art, without departing from the nature and scope of the invention, as defined in the appended claims. e

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A corrosion resisting connection between plates of a structure subjected to hydrodynamic and aerodynamic fluid flow comprising a plurality of overlapping sheet metal plates having registering perforations therein, adjacent plates having inwardly depressed areas surrounding said perforations forming substantially conical depressions on the outer surfaces of said plates and substantially conical protuberances on the inner surfaces thereof, the protuberances on the inner surface of an outer plate being disposed in nested relation with the depressions in an adjacent inner I plate; and fastening elements extending through said perforations and having outer head portions disposed entirely within the depressions in the outermost of said plates and spaced from they plane of the surfaces of said outermost plates and inner head portions in engagement with the conical protuberance of the innermost of said plates.

2. A corrosion resisting connection between.

plates of a structure subjected to hydrodynamic and aerodynamic fluid flow comprising a plurality of overlapping sheet metal plates having registering perforations therein, adjacent plates having inwardly depressed areas surrounding said perforations forming substantially conical depressions on the outer surface of said plates and substantially conical protuberances on the inner sure faces thereof, the protuberances on the inner surface of an outer plate being disposed in nested relation with the depressions in an adjacent inner plate; and fastening elements extending through said perforations and having outer head portions disposed entirely within the depressions in the outermost of said plates and spaced from the:

plane of the surfaces of said outermost plates and inner head portions in engagement with the.

conical protuberance of the innermost of said plates.

3. A corrosion resisting connection between plates of a structure subjected to hydrodynamic, and aerodynamic fluid flow comprising a plurality of overlapping sheet metal plates having registering perforations therein, adjacent plates having inwardly depressed areas surrounding said perforations forming substantially conical depressions on the outer surfaces of said plates and substantially conical protuberances on the,

inner surfaces thereof, the protuberances on the spaced from the plane of the surfaces of said outermost plates and inner head portions in engagement with the conical protuberance of the innermost of said plates; and a protective coating. covering the outer surface of the outermost of said members and the outer head portions of said fastening elements, whereby an additional quantity of said coating will collect in saidde- "m auaaee pressions adjacent to the line of contact between said outer head portions and said outermost member.

4. The method of connecting the plates of a structure subjected to hydrodynamic and aerodynamic fluid flow which comprises arranging the plates with adjacent marginal portions thereof disposed in overlapping relation; forming registering perforations in said overlapping marginal portions; depressing said plates in an area surrounding said perforations to provide recesses on their outer surfaces and protuberances on their inner surfaces; inserting rivets provided with preformed head portions having outer anodic protective films thereon in said perforations with said head portions disposed entirely within the recesses of the outermost of said plates and spaced from the plane of the surfaces of said outermost plates; and upsetting the inner ends of said rivets to form inner head portions engaging the protuberances on the innermost of said plates, whereby-the anodic film of said preformed head portions are preserved against rupture.

5. The method of connecting the plates of a structure subjected to hydrodynamic and aerodynamic fluid flow which comprises arran ing the plates with adjacent marginal portions thereof disposed in overlapping relation; forming registering perforations in said overlapping marginal portions; depressing said plates in an area surrounding said perforations to provide r on their outer surfaces and protuberances on their inner surfaces; insertins rivets having preformed head portions in said perforations with said heads disposed entirely within the recesses of the outermost of said plates and spaced from the plane of the surfaces of said outermost plates; and upsetting the inner ends of said rivets to form inner head portions engaging the protuberances on the innermost of said plates, and conforming closely with the configuration thereof.

6. The method of connecting the plates of a structure subjected to hydrodynamic and aerodynamic fluid fiow which comprises arranging head portions engaging the protuberances on theinnermost of said plates, and coating the outer surfaces of the outermost of said members and the outer head portions of said rivets with a corrosion resisting material, whereby an additional quantity of said material will collect in said recesses adjacent to the line of contact between said outer head portions and the outermost of said plates.

' NICHOLAS A. DRAIM. 

